1. Field of the Invention
The present invention relates to a wireless local area network (WLAN), and more particularly, to a voice over Internet protocol (VoIP) system and related WLAN device applicable for a WLAN.
2. Description of the Prior Art
As Internet technology advances, Internet-based applications are more and more popular. Voice over Internet protocol (VoIP) and video over Internet protocol, for example, are two common technologies.
After connected to an Internet, a device can perform voice communication with another device through the Internet by VoIP related technology. Such devices include, but not limited to, personal computers and notebook computers that can be connected to the Internet directly by wires. As technology advances, devices not directly connected to the Internet, such as mobile phones and traditional phones (i.e. public switched telephone network (PSTN) phones) can also perform voice communication by VoIP related technology in an indirect manner.
In the prior art utilizing VoIP technology, for example, VoIP software can be executed by a computer to perform voice communication with a remote device. In such a case, an earphone and a microphone are required to play/capture audio information. After users connect the earphone and the microphone to the computer by some physical wires, audio information generated by the VoIP software can be sent to the earphone for play, and audio information captured by the microphone can be sent to the VoIP software for processing. Since every physical wire has inherently a fixed length, the above example of the prior art thus has limitations in use. Those limitations, for example, include limited mobility of the earphone and the microphone. Conventionally, physical wires cannot transmit control information, so users have to use additional input/output (I/O) interface devices (such as mouse and keyboards) for the computer to achieve control operations (such as number input). Limited by the prior art, user scenarios are hard to be expanded by architecture designers.
Additionally, in another example of the prior art, a wireless earphone and a wireless microphone are provided for playing/capturing audio information. In this example, a computer executes VoIP software to perform voice communication with a remote device, and the wireless earphone and the wireless microphone communicate wirelessly with the computer through related wireless interfaces. The wireless interfaces include, for example, proprietary radio frequency (RF) interfaces, digital enhanced cordless telecommunications (DECT) interfaces, and Bluetooth interfaces. Due to low transmission rates and short transmission distances of the above-mentioned wireless interfaces, architecture designers may encounter some technical limitations when designing user scenarios.
In the prior art, an integrated VoIP phone is also provided. FIG. 1 is a schematic diagram illustrating an example of a software architecture of a VoIP phone 100 of the prior art. As shown, the software architecture of the VoIP phone 100 comprises four layers as follows: a user interface finite state machine (UI FSM) layer 120, a middle-ware layer 140, a real time operating system (RTOS) layer 160, and a device driver layer 180.
The UI FSM layer 120, as an example, comprises a plurality of FSMs for call control 121, handset setup 122, VoIP setup 123, and phone book management 124. The RTOS layer 160 operates on a transmission control protocol/Internet protocol (TCP/IP) 161. The device driver layer 180 comprises a network card driver 181, a screen driver 182, an audio interface driver 183, a general-purpose input/output (GPIO) interface driver 184, a universal serial bus (USB) driver 185, and a flash memory driver 186.
The VoIP phone 100 is connected to the Internet through an access point (AP) and is able to perform VoIP related controls and operations independently. The middle-ware layer 140 of the VoIP phone 100 thus has a complicated software architecture. Specifically, the middle-ware layer 140 takes charge of tasks corresponding to session initiation protocol (SIP) 141, network address translation traversal (NAT-T) 142, real time streaming protocol (RTSP) 143, real time transport control protocol (RTCP) 144, resource reserve protocol (RSVP) 145, differentiated services (DiffServ) 146, audio protocol (e.g. G.711 audio codec protocol) 147, quality of service (QoS) 148, real time transport protocol (RTP) 149, and others. Additionally, SIP 141 takes charge of addressing, capability exchange, registration, call setup, and others. QoS 148 takes charge of packet reordering, adaptive jitter compensation, packet lost handling, flow control, echo cancellation, and others. RTP 149 takes charge of payload type identification, sequence numbering, time stamping, delivery monitoring, and others.
As described, the VoIP phone 100 has a complicated software architecture, especially in the middle-ware layer 140. To achieve related complicated computation, the VoIP phone 100 should be implemented by high-level hardware, thereby increasing overall cost. Additionally, complicated computation causes large power consumption and thus decreases available power-on/standby duration for the VoIP phone 100. In conclusion, although the VoIP phone 100 of the prior art has a good mobility, its high price and excessive power consumption are two major drawbacks that repel common consumers.